SRS Transmission in LAA Cells via Dynamic Subframe Selection
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Solution Overview
Problem
Current wireless communication systems face challenges in efficiently managing Sounding Reference Signals (SRS) in multicarrier communication systems, particularly in scenarios involving carrier aggregation and Licensed Assisted Access (LAA), where existing methods struggle with optimal SRS transmission timing and resource allocation, leading to potential interference and reduced network efficiency.
Innovation Solution
The proposed solution involves a method for dynamically configuring SRS transmission in Licensed Assisted Access (LAA) cells, using aperiodic SRS triggers and multi-subframe grants, where the wireless device performs listen-before-talk (LBT) procedures to determine available subframes for SRS transmission, optimizing SRS subframe selection based on RRC configuration parameters and LBT outcomes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If aperiodic SRS triggers are used in LAA cells with multi-subframe grants, then uplink radio efficiency is improved and control signaling overhead is reduced, but SRS transmission timing coordination becomes more complex due to LBT procedures
Solution Approach 1:
The patent implements dynamic SRS transmission timing by allowing the wireless device to adaptively determine SRS subframe positions based on LBT outcomes. The SRS transmission is no longer fixed but dynamically adjusted according to channel access success, enabling efficient utilization of available uplink resources while maintaining coordination through predefined RRC configuration parameters that guide the dynamic selection process
Solution Approach 2:
The patent applies preliminary action by configuring RRC parameters in advance that define the rules for SRS subframe selection. These pre-configured parameters include offsets and validity conditions that the wireless device uses to determine SRS transmission timing before actual LBT execution, reducing real-time coordination complexity while maintaining flexibility
2Productivity
If SRS transmission is optimized based on LBT outcomes, then network efficiency is improved, but interference management in unlicensed spectra becomes more challenging
Solution Approach 1:
The patent implements feedback mechanisms where the wireless device monitors LBT outcomes and adjusts SRS transmission timing accordingly. The base station receives SRS transmissions at optimized times and can adjust future scheduling based on channel conditions and interference levels observed, creating a closed-loop system that improves network efficiency while managing interference through adaptive response to actual channel state
Solution Approach 2:
The patent utilizes periodic action by configuring SRS transmissions to occur at specific periodic intervals defined by RRC parameters, while allowing these periodic transmissions to be gated by LBT success. This maintains regular SRS sampling for channel state information while ensuring transmissions only occur when channel conditions permit, thereby improving efficiency and reducing interference simultaneously
3Adaptability or versatility
If multiple carriers are operated seamlessly, then carrier aggregation performance is improved, but SRS resource allocation across carriers becomes more complex
Solution Approach 1:
The patent applies segmentation by treating SRS resource allocation on each carrier independently through separate RRC configuration parameters for each serving cell. Each carrier's SRS transmission timing and resources are configured and managed separately, allowing seamless carrier aggregation operation while simplifying the overall allocation complexity through modular, cell-specific configuration management
Data Source
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AI summary
A wireless device receives a downlink control information (DCI) indicating uplink resources in one or more subframes. The DCI comprises a field indicating a position of a subframe in the one or more subframes for transmission of a sounding reference signal (SRS). The wireless device transmits the SRS in the subframe.